Mastering Japanese Politeness: Using ~Desu and ~Masu

Japanese has different levels of politeness based on who you are talking to. Imagine a ladder. The bottom rung is "casual" (talking to your cat). The top rung is "honorific" (talking to the Emperor). ~Desu and ~Masu sit comfortably right in the middle. They bridge the gap between people who aren't best friends yet.

• Desu is used with nouns and adjectives. It essentially means "is," "am," or "are."
• Masu is used with verbs. It turns an action into a polite statement.

When you use these, you are showing that you recognize the other person’s space and status. It’s like a verbal handshake. You aren't being overly stiff, but you aren't being rude either. Most textbooks start here because if you master this, you can survive 95% of social interactions in Japan without offending anyone. It’s like a grammar traffic light—green means go, and these suffixes are your green light.

1. 1For Nouns: Simply add desu after the noun.
2. 2Example: Gakusei (student) + desu = Gakusei desu (I am a student).
3. 3For Adjectives:
4. 4i-adjectives: Add desu after the dictionary form. Oishii (delicious) + desu = Oishii desu.
5. 5na-adjectives: Add desu after the word. Kirei (pretty) + desu = Kirei desu.
6. 6For Verbs (~Masu):
7. 7Identify the verb stem.
8. 8For Group 1 (U-verbs): Change the final -u sound to an -i sound, then add masu.
9. 9Iku (go) -> Iki + masu = Ikimasu.
10. 10For Group 2 (Ru-verbs): Remove the final ru and add masu.
11. 11Taberu (eat) -> Tabe + masu = Tabemasu.
12. 12For Irregular Verbs: Just memorize them (there are only two!).
13. 13Suru (do) -> Shimasu.
14. 14Kuru (come) -> Kimasu.

You should use this style with anyone you don't know well. This includes shop staff, teachers, older colleagues, and even people your own age you just met.

• Ordering Food: When the waiter asks what you want, say Kore o kudasai (This please) and Oishii desu (It's delicious) afterward.
• Asking Directions: Start with Sumimasen (Excuse me) and end your sentences with desu or masu.
• Job Interviews: Even if the job is casual, start with this polite level. It shows you have manners.
• At the Office: Your boss and coworkers expect this level of respect.

Basically, if you aren't 100% sure you are "best friends" with someone, stick to desu and masu. It’s much better to be "a bit too polite" than "accidentally a jerk." Think of it as wearing a clean shirt to a nice dinner—it’s just the right thing to do.

Don't use these with your family, your close friends, or your pets. If you tell your dog O-sanpo ni ikimasu (I am going for a walk) in the polite form, he might think you’ve become a stranger!

• With Family: It sounds distant. Your mom might ask why you're being so formal.
• With Close Friends: It can feel like you're putting up a wall. It’s a bit like calling your best friend "Sir" or "Ma'am."
• In Manga/Anime: Characters often skip this to sound cool or tough. Don't copy them in real life unless you want to sound like a cartoon villain.

Yes, even native speakers mess this up sometimes, usually when they are tired or angry, but as a learner, staying polite is your safest bet. If a friend tells you "Hey, you don't need to be so polite," that’s your cue to switch to the casual form. Until then, keep the desu train rolling.

• Mixing Levels: Don't start a sentence politely and end it casually. It’s jarring for the listener. Pick a lane and stay in it!
• Double Politeness: You don't need to add desu after a verb that already has masu. Tabemasu desu is a big no-no. It’s like saying "I am eating am."
• Forgetting the Verb Stem: Beginners often try to say Iku-masu. Remember to change that vowel sound for Group 1 verbs! It should be Ikimasu.
• Over-using 'Desu' with Verbs: Desu is not a universal glue. It doesn't belong after dictionary-form verbs. Use masu for actions and desu for descriptions.
• The 'Na' Trap: For na-adjectives, you don't need the na when using desu. It’s Shizuka desu, not Shizuka na desu.

The biggest contrast is the "Plain Form" (Dictionary Form).

• Polite: Tabemasu (I eat/will eat).
• Plain: Taberu (I eat/will eat - casual).

While they mean the same thing, the social impact is massive. Plain form is for your inner circle. Polite form is for the world. There is also a "Super Formal" (Keigo) level, which uses different words entirely (like Itadakimasu instead of Tabemasu). You’ll learn that much later. For now, focus on the "Teineigo" (Desu/Masu) as your primary tool. It’s the Swiss Army knife of Japanese grammar. It’s reliable, functional, and everyone understands it. If the Plain Form is a t-shirt and Keigo is a tuxedo, Desu/Masu is a nice button-down shirt. Perfect for almost every occasion.